This application claims the benefit of Japanese Application No. 2002-127854 filed Apr. 30, 2002.
The present invention relates to a through terminal and an X-ray tube, particularly a through terminal for electric connection between the inside and the outside of a hermetically sealed vessel, as well as an X-ray tube having such a through terminal.
The interior of an X-ray tube is held in vacuum. The supply of voltage and current to an internal electrode of an X-ray tube is performed through a through terminal. The through terminal has a hermetically sealed structure. The through terminal is made up of a tubular member, an electrically insulating plate member bonded in a hermetically sealed state to an inner periphery of the tubular member, and an electrically conductive pin extending through the plate member in a hermetically sealed state. The bonding of the components for ensuring a hermetic seal is performed by soldering. The soldering is performed by applying high temperature.
In a through terminal of an X-ray tube, since a plate member is constituted by glass, the air-tightness is apt to be impaired by the influence of, for example, a residual stress of after soldering.
Therefore, it is an object of the present invention to realize a through terminal capable of maintaining air-tightness stably and an X-ray tube having such a through terminal. The through terminal according to the present invention is applicable widely to uses in which the inside and the outside of a hermetically sealed vessel are connected with each other electrically.
According to the present invention, for solving the above-mentioned problem, there is provided a through terminal comprising a tubular member, a plate member formed of an insulating ceramic material and bonded to an inner periphery of the tubular member in a hermetically sealed state, and a pin formed of an electrically conductive material and extending through the plate member, the portion of the pin which portion extends through the plate member being located inside a metallic tube and the pin being bonded to the plate member in a hermetically sealed state through the metallic tube.
In the present invention, the plate member is constituted by an insulating ceramic material and the pin formed of an electrically conductive material and extending through the plate member is disposed so that its portion extending through the plate member is located inside a metallic tube and bonded to the plate member in a hermetically sealed state through the metallic tube. Consequently, it is possible to realize a through terminal capable of maintaining air-tightness stably.
To make positioning easy, it is preferable that the tubular member have on its inner periphery a stepped portion for abutment thereagainst of a plate face of the plate member.
To make bonding of the plate member, it is preferable that the tubular member be formed of an alloy comprising at least iron, nickel, and cobalt.
Likewise, to make bonding of the plate member easy, it is preferable that the tubular member be formed of stainless steel.
To maintain air-tightness stably, it is preferable that the X-ray tube have a through terminal of the foregoing construction.
According to the present invention, it is possible to realize a through terminal capable of maintaining air-tightness stably and an X-ray tube having such a through terminal.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.